The wiki in this thread says that Fred Meyer doesn't count (I presume because their stores are primarily supercenters). Before Kroger acquired Fred Meyer, it expanded into Utah and built a few of their supercenters. In 1997, Fred Meyer acquired the Smiths grocery chain. Following that, Fred Meyer rebranded its Fred Meyer stores as Smiths Marketplace in states where Smiths was the much larger brand. Utah was one of those states. And then Kroger acquired Fred Meyer (and thus also Smiths).

So, I am assuming that AMEX has no problem giving 6% on the Blue Cash Preferred card for the regular Smiths grocery stores. Does anyone have any experience getting (or not) the full 6% at Smiths Marketplace stores? Asking because a Smiths Marketplace store is where we do the great majority of our grocery shopping. FWIW, Smith's Marketplace is not a separate brand of Kroger, but is instead a sub-brand of Smiths.

Also, FWIW, when we use our Chase Freedom Unlimited card at Smith's Marketplace the transaction Merchant Type is "Grocery Stores and Supermarkets" (which doesn't matter for that card since it is a flat 1.5% everywhere). I don't believe that I have ever used an AMEX at Smith's Marketplace, however. I could make a small purchase there using my Delta Skymiles Gold AMEX to see how it shows up. If it shows up as a supermarket with the Delta card, is it guaranteed that it would also show up that same way with the Blue Cash Preferred card?